Bottles or similar containers can be used for liquids, e.g. for beverages. The containers can be made of a transparent or translucent material, for example of glass, or of a translucent plastic, e.g. PET. Glass bottles, in particular, can have different colorings with, for example, brown and green but also blue bottle colors mentioned only as examples. The bottles, or similar containers are guided, when empty, preferably after they have been cleaned, on a transporter past the inspection device. It is known that bottles can also be closed with so-called crown caps or other oxidizable capping elements. In that regard, it is possible that the crown cap will have oxidized and thus that rust from the crown cap, or from another oxidizable capping element, will be deposited in the mouth region of the bottle. If the inspection device detects deposited rust, although the empty bottle has passed the cleaning device, the bottle concerned is rejected from the bottle flow, at a suitable location, and either destroyed or re-enters the bottle flow before the cleaning system.
Normally, the lighting unit emits a light of the same spectrum, thus in the same color, which is why the inspection device does not always achieve a reliable inspection result for bottles of different colors. Hence, it is possible for a bottle that has rust to be mistakenly classified as a good bottle, even though the bottle should have been separated out due to the existing contamination. If such a bottle enters the further production process, this can lead to unproductive downtime, as the filled product, from a hygienic perspective, will not be perfect due to the possible contact with the contamination. If such a bottle reaches the consumer, the maker of the product, or the system manufacturer, can furthermore suffer substantial damage.